Terms Allowed in Spectroscopic Structure of Calcium

1. The problem statement, all variables and given/known data
Why can't we have 4s^2 3S1 calcium? I've looked up a table of terms and this is never given, so I guess we can't have it. Why can't the spins of each of the outer electrons add to give S = 1, J = 1, and a degeneracy of 3? I guess the answer must be pretty basic since nobody has asked about this that I can find, so what's going on?